1. Field Of The Invention
The present invention broadly relates to methods of making ceramic composite structures. In particular, the invention relates to reservoir feed methods of making ceramic composite structures comprising a polycrystalline ceramic matrix embedding a filler.
2. Description of Commonly Owned U.S. Patent Applications
The subject matter of this application is related to that of Commonly Owned U.S. patent applications Ser. No. 819,397, filed Jan. 17, 1986 as a continuation-in-part of Ser. No. 697,878, filed Feb. 4, 1985, both in the name of Marc S. Newkirk et al and entitled "Composite Ceramic Articles and Methods of Making Same." This application discloses a novel method for producing a self-supporting ceramic composite by growing an oxidation reaction product from a parent metal into a permeable bedding of filler. However, the method does not provide for imparting a pre-selected shape or geometry to the resulting composite.
The method of growing ceramic oxidation reaction product is disclosed generically in Commonly Owned U.S. Pat. No. 4,713,360 which issued on Dec. 15, 1987 from U.S. patent application Ser. No. 818,943, filed Jan. 15, 1986, as a continuation-in-part of Ser. No. 776,964, filed Sept. 17, 1985, as a continuation-in-part of Ser. No. 705,787, filed Feb. 26, 1985 as a continuation-in-part of Ser. No. 591,392, filed Mar. 16, 1984, all in the name of Marc S. Newkirk et al and entitled "Novel Ceramic Materials and Methods of Making The Same." This discovery of an oxidation phenomenon, which may be enhanced by the use of a dopant alloyed in the parent metal, affords self-supporting ceramic bodies of desired size grown as the oxidation reaction product of the precursor parent metal.
The foregoing method was improved upon by the use of external dopants applied to the surface of the precursor parent metal as disclosed in Commonly Owned U.S. patent applications Ser. No. 822,999, filed Jan. 27, 1986, as a continuation-in-part of Ser. No. 776,965, filed Sept. 17, 1985 as a continuation-in-part of Ser. No. 747,788, filed Jun. 25, 1985 as a continuation-in-part of Ser. No. 632,636 filed Jul. 20, 1984, all in the name of Marc S. Newkirk et al and entitled "Methods of Making Self-Supporting Ceramic Materials".
Further developments of the foregoing methods enable the formation of ceramic composite structures which (1) contain therein one or more cavities which inversely replicate the geometry of a shaped precursor parent metal, and (2) have a negative pattern which inversely replicates the positive pattern of a parent metal precursor. These methods are described, respectively, (1) in Commonly Owned U.S. patent application Ser. No. 823,542 filed Jan. 27, 1986, in the name of Marc S. Newkirk et al, entitled "Inverse Shape Replication Method of Making Ceramic Composite Articles and Articles Obtained Thereby", and (2) in Commonly Owned U.S. patent application Ser. No. 896,157, filed Aug. 13, 1986 in the name of Marc S. Newkirk and entitled "Method of Making Ceramic Composite Articles With Shape Replicated Surfaces and Articles Obtained Thereby".
Also, methods of making ceramic composite structures having a pre-selected shape or geometry were developed. These methods include the utilization of a shaped preform of permeable filler into which the ceramic matrix is grown by oxidation of a parent metal precursor, as described in Commonly Owned U.S. patent application Ser. No. 861,025, filed May 8, 1986, in the name of Marc S. Newkirk et al and entitled "Shaped Ceramic Composites and Methods of Making the Same". Another method of making such shaped ceramic composites includes the utilization of barrier means to arrest or inhibit the growth of the oxidation reaction product at a selected boundary to define the shape or geometry of the ceramic composite structure. This technique is described in Commonly Owned U.S. patent application Ser. No. 861,024, filed May 8, 1986, in the name of Newkirk et al and entitled Method Of Making Shaped Ceramic Composites With The Use Of A Barrier.
The entire disclosures of all of the foregoing Commonly Owned U.S. Patent Applications and Patent are expressly incorporated herein by reference.
3. Background and Prior Art
In recent years, there has been increasing interest in the use of ceramics for structural applications historically served by metals. The above-noted Commonly Owned U.S. Patent Applications provide a significant advance in the art, particularly with respect to cost-effective production of high strength, fracture-tough ceramic and ceramic composite bodies. The techniques of the Commonly Owned U.S. Patent Applications enable the production of ceramic composite structures, including shaped ceramic composite structures and large ceramic structures, by utilizing an unusual oxidation phenomenon which permits by-passing the use of powder sintering and hot pressing technologies and their inherent limitations. For example, the necessity in such conventional powder technologies to densify the powder bodies as by compaction or pressing is incompatible with the manufacture of large, one-piece ceramic structures. Further, such powder processing technologies do not readily lend themselves to the preparation of ceramic composite structures. Ceramic composite structures comprise a heterogeneous material, body or article made of two or more different materials which are intimately combined in order to attain desired properties of the composite. Typically it comprises a ceramic matrix which embeds one or more diverse filler materials such as particulates, rods, fibers or the like.
The present invention is based on the use of one or more of the techniques of the Commonly Owned U.S. Patent Applications and U.S. Patent, further improved upon by providing a parent metal reservoir means as further described herein. These techniques overcome the above-described difficulties by producing high strength and fracture-tough ceramic microstructures by a mechanism which is more direct and less expensive than conventional approaches. The present invention provides further improved methods and means for reliably producing ceramic composite structures based on oxidation reaction products, of a size and thickness which is difficult or impossible to duplicate with prior technology. The present invention also allows the production of ceramic-surfaced metallic structural components which in certain cases are lighter in weight and lower in cost than many all-ceramic bodies.